6.4 Ovarian Hyperstimulation Syndrome

Question 1

When do you get OHSS?

Answer 1

Happens during IVF

Question 2

Which hormone is implicated in OHSS?

Answer 2

hCG given at final step of follicle maturation

Question 3

What are the features of OHSS?

Answer 3

Early OHSS presents within 7 days of the hCG injection. Late OHSS presents from 10 days onwards.

Features of the condition include:

Abdominal pain and bloating
Nausea and vomiting
Diarrhoea
HYPOTENSION
Hypovolaemia
ASCITES
Pleural effusions
Renal failure
Peritonitis from rupturing follicles releasing blood
Prothrombotic state (risk of DVT and PE)

Question 4

What is the pathophysiology of OHSS?

Answer 4

In IVF se of gonadotropins LH and FSH means many follicles develop
–> trigger injection of hCG for maturation36hr before collection
–> hCG stumulates VEGF release from granulosa cell in follicles
–> VEGF causes incr vascular perm
–> fluid leaks from capillaries
–> oedema, ascites, hypovolaemia

There is also RAAS activation. Expect raised renin.

Question 5

What hormone level correlates with OHSS severity?

Answer 5

renin

Question 6

What are the risk factors for OHSS?

Answer 6

• Younger age
• Lower BMI
• Raised anti-Müllerian hormone
• Higher antral follicle count
• PCOS
• Raised oestrogen levels during ovarian stimulation

Question 7

How can we prevent OHSS?

Answer 7

1. Assess each woman for individual risk
2. When stimulating with Gonadotropins measure:
   - oestrogen (inc is inc risk)
   - US (large and many follicles is inc risk)
3. If at high risk then:
   - Use of the GnRH antagonist protocol (rather than the GnRH agonist protocol)
   - Lower doses of gonadotrophins
   - Lower dose of the hCG injection
   - Alternatives to the hCG injection (i.e. a GnRH agonist or LH)

Question 8

What are the clinical features seen in each severity of OHSS?

Answer 8

Mild: Abdominal pain and bloating

Moderate: Nausea and vomiting with ascites seen on ultrasound

Severe: Ascites, low urine output (oliguria), low serum albumin, high potassium and raised haematocrit (>45%)

Critical: Tense ascites, no urine output (anuria), thromboembolism and acute respiratory distress syndrome (ARDS)

Question 9

How do you manage OHSS?

Answer 9

Supportive and treat complications:

• oral fluids and urine monitor
• LMWH
• poss paracentesis to remove ascites
• IV colloids eg HAS

Mild can be outpatient, severe may be ICU.

Raised haematocrit suggests dehydration